Hi there, someone gave me a 400W HPS bulb with external igniter: https://www.any-lamp.com/osram-vialox-e40-nav-t-400w-super-4y-4050300281179

and I want to try it if it works

I only have 250W core and coil ballast (the normal non-electronic one also called a choke) with an igniter setup

because this things are big (my floodlight that this is all housed in is big) I cannot just buy a 400W one, because I will run out of space  so I have to do with what I have

Now I did read that if u do the other way around (250W bulb on 400W ballast) the bulb might explode, because nothing is limiting the current

But what about 400W bulb, 250W ballast, can I damage my ballast and igniter (I realy don't want to do that, because it took me months to find this (with coil and core ballast) floodlight locally)

Can I also run any other bulbs with my ballast (the guy that gave me the HPS (he also had 400W fixture, but sadly he took out the ballast and left the fixture for gypsies, he didn't know anyone would want that nowadays) also said he has some Mercury Vapor and CHM ones, here is a picture if anyone is curious

Igniter: https://imgur.com/gAqFgTX
Ballast: https://imgur.com/YF42Qop

On ballast it says: Layrton HSI-SAPI 250/23-P and here is its manual: https://fenyaruhaz.hu/dtradeFS/LAYR/INFO/HSI-SAPI_250_23-24.pdf
some other document: https://www.dna.cz/download/ke-stazeni/Layrton/Katalogov%E9%20listy/Tlumivky%20v%FDbojky/02_layrton_sodik_halogenold.pdf

The lamp would be underdriven and the ballast would overheat.

even the choke and core one (I thought this things are resilient little bastards that last a lifetime)?

Yes.